Re: why is hard water so called?

Good question - most texts are silent on the subject and it is not possible
for me to give a definitive answer. Sorry.

According to Ramsden (1994, p151) "With some types of tap water it is
hard to get a lather, and such water is described as hard." This is a rather 
lame explanation as presumably with soft water "it is soft to get a lather". 
See? It doesn't really make sense.

I have heard that hard water feels noticeably different from soft water when
you try to soap yourself with it. This sounds a more likely explanation - the 
calcium-soap scum would feel rather gritty.

A wild guess would be that because hard water can form deposits of 
calcium salts in kettles, pipes and the like it is in reference to this ability to 
form hard deposits that hard water is named.

Take your pick!

Ewen McLaughlin, Lecturer in Chemistry

Ref:
Ramsden, E.N, Chemistry for GCSE Simon & Schuster, 3rd ed , 1994